US scientists say they have duplicated the generation of new adult brain cells in the lab in a controlled way.

It is hoped the technique, tested so far on animal cells, will eventually allow scientists to produce a limitless supply of a person's own brain cells.

The researchers believe they could potentially be used to treat disorders like Parkinson's disease and epilepsy.

The study, by the McKnight Brain Institute, is published in Proceedings of the National Academy of Sciences.

The ability to regenerate the needed cell type and placing it in the correct spot would have major impact

Dr Eric Holland

It is not the first time that immature stem cells have been manipulated in the laboratory to become brain cells.

But the researchers say nobody else has replicated the process of cell maturation that goes on in the brain in such complete and close step-by-step detail before.

However, a leading British expert has stressed the importance of not hyping the potential of work in this field.

The researchers harnessed a technique which had already been used to produce adult blood cells outside the body.

They collected immature neural stem cells at a primitive stage of development from mice and used chemicals to induce them to mature.

During the process they snapped images of the cells every five minutes using a special microscope.

This enabled them to create a short film showing the cells developing stage by stage into fully fledged adult brain cells (neurons).

They were also able to track the physiological changes that take place during development in closer detail than ever before.

Passing through brain

A little more than a decade ago, scientists came to realise that the brain continues to produce small amounts of new cells even in adulthood.

Stem cells develop naturally into fully fledged brain cells as they travel through a neural pathway that begins deep within the brain in a region called the sub ventricular zone, and ends in an area called the olfactory bulb.

However, the latest study showed that the cells could still develop in the normal way away from their usual environment inside the brain.

Researcher Dr Bjorn Scheffler said: "We can basically take these cells and freeze them until we need them.

"Then we thaw them, begin a cell-generating process, and produce a ton of new neurons."

Dr Eric Holland, a neurosurgeon at Memorial Sloan-Kettering Cancer Center in New York, said: "As far as regenerating parts of the brain that have degenerated, such as in Parkinson's disease, Huntington's disease and others of that nature, the ability to regenerate the needed cell type and placing it in the correct spot would have major impact."

However, Dr Jim Cohen, of the UK's Medical Research Council Centre for Developmental Neurobiology, told the BBC News website: "This work does represent a technical advance but it's relatively minor and not especially novel.

"More importantly, as is the case for all tissue culture models, they are a long way from showing that such cells could be of therapeutic potential."